Tag Archives: David Yarbrough

Barndominium High R-Value Overhead Doors Part II

Continuing the discussion of high R-values in overhead doors from yesterday’s Part I:

Are reported R-values even accurate?

There’s another potential problem with R-values reported by garage-door manufacturers: even if one accepts advertised R-values represent center-of-panel values rather than whole-door values, these numbers are still higher than most insulation experts believe are possible.

Several manufacturers report their polyurethane-insulated door panels have R-values between R-8.6 and R-9.0 per inch — values highly unlikely if not technically impossible, even for door panel centers.

“The R-value of polyurethane decreases with age,” said Yarbrough. “When it is absolutely fresh you might get R-7.5 per inch, but a realistic aged R-value would be lower — perhaps about R-6.5 per inch would be on the high end. I’m not sure I can explain these reported test results. I have seen labs make mistakes before. I think it’s an error.”

What about air leakage?

If garage-door manufacturers ever decide to report whole-door U-factors or whole-door R-values — an important piece of this door-rating puzzle will still be missing. Why? When it comes to thermal performance of garage doors, air leakage matters much more than R-value.

“Garage doors are so leaky that they are difficult to test,” Thoman said. “Their leaks exceed the capabilities of the available testing apparatus.”

When he needed to buy a garage door for his own house, Thoman ignored advertised R-values. “I find it almost offensive that garage-door manufacturers even publish the R-value of the insulation material,” Thoman told Holladay. “I hate it when I see that, because it’s not a representation of the door’s performance. Air leakage is a much more important issue than the R-value of the door.”

Bottom line

Although some garage-door manufacturers have measured whole-door U-factor and air-leakage characteristics of their doors, most won’t release their data. Until they do, purchasers of garage doors have to select their doors based on anecdotes.

Unfortunately, Sectional Garage Doors can’t be installed air tight, there needs to be room for door to slide up and down against door jambs.  These little spaces let cold air draft in and negate much insulating done in door construction.

Some drafts can be stopped with a vinyl weather seal around door and bottom seal, or astragal, can fill in spaces along door bottom depending on how level and even floor is.

Back to why your barndominium needs an insulated overhead door.

More insulation, of course. An uninsulated overhead door is barely a step above an open hole in your wall.

A stronger, more rigid door.  Both polystyrene sandwich doors and polyurethane doors are bonded to steel skin to make them stronger.  They hold up to better to moderate abuse. Be realistic, there is no door which will hold up to a vehicle bumper.

They are much quieter.  This bonding eliminates most rattling which comes with pan (uninsulated steel) doors or as they are referred to as ‘Beer Can Doors”.   

And, while you are at it, make sure your insulated overhead door is appropriately wind load rated: http://www.hansenpolebuildings.com/2014/12/wind-load-rated-garage-doors/.

Barndominium High R-Value Overhead Doors Part I

Barndominium High R-value Overhead Doors
When my lovely bride and I had our post frame building shouse (shop house aka barndominium) constructed, energy efficiency was important for us. Then Hansen Pole Buildings was ordering our overhead doors through my friend David Vance, owner of Rainer Building Products in Western Washington. I approached David with our needs for doors and he recommended C.H.I. doors with an advertised R value of 17.19 for an 1-7/8” thick polyurethane insulated door.
Unfortunately, these advertised R-values are almost meaningless.

Advertised R-values are inaccurate, irrelevant — or both

To determine thermal performance of a garage door, you need to know two things:

A door’s leakiness, and entire door assembly R-value or U-factor.

R-values claimed by garage-door manufacturers are measured at door panel centers. Apparently no manufacturer reports R-value of their entire door panel (including panel edges, seams between panels, and door perimeter) in their promotional materials. Moreover, manufacturers’ reported R-values tell us nothing about air leakage.

Most garage-door manufacturers are reluctant to share actual laboratory reports showing results of R-value testing.

“For marketing purposes, the garage door people get a measurement on the center of panel,” said David Yarbrough, a research engineer and insulation expert at R&D Services in Cookeville, Tennessee. “The overall R-value of the entire door might be quite a bit less — in extreme cases, it may be half — of the R-value of the center of the panel. Not everyone approves of this kind of marketing. It’s been a hot debate in recent years.”

In fact, real percentages turn out to be much less than half.

Actual R-values are one-third the advertised values

Although it’s hard to obtain actual test results reporting whole-door U-factors of “tested installed doors,” Martin Holladay managed to obtain one report on a garage door from Clopay, and another on a garage door from Overhead Door.

Clopay provided test results for their model 3720 five-panel garage door. According to Mischel Schonberg, Clopay’s public relations manager, their door is insulated with two inches of polyurethane foam. Schonberg wrote, “This model is the commercial version of our residential model 9200 and has the same construction.”

While Clopay advertises their 9200 door is R-17.2 — presumably, a claim based on a center-of-panel measurement — actual test report for an installed door shows R-6.14.
While Overhead Door advertises their model 494/495 Thermacore door has an R-value of 17.5 — a claim, like competitors’ claims, is presumably based on a center-of-panel measurement — installed door test reports show a U-factor of 0.16, equivalent to R-6.25.

Based on these only two test reports Martin was able to track down, it seems logical to conclude R-value of a garage door is about one-third of R-value claimed in a manufacturer’s brochure.

All over the map

Mike Thoman, director of thermal testing and simulation at Architectural Testing Incorporated, a Pennsylvania laboratory, has tested many garage doors.

“The assembly R-values are not going to be nearly as good as the R-value of the material would indicate,” Thoman told Holladay. “When you compare the assembly R-value to the material R-value, the percentages are all over the map. The percentage is a function of how the joints in the panels are made, and whether any attempt was made to provide for thermal breaks at panel edges — a lot of different things. Some products have a lot of insulation in the panel but have everything else wrong. We’ve also seen doors that do everything right. There’s really a wide, wide range.”

Come back tomorrow for Part II in this discussion of R-values in overhead doors.